Solar ultraviolet (UV) radiation is a major environmental skin carcinogen that induces DNA damage and modulates a variety of genes that regulate cell growth, proliferation and apoptosis. The transcriptional regulation of genes is part of the cellular reaction that operates as a defense mechanism against the adverse effects of UV radiation. MicroRNAs (miRNA) are a group of small non-coding RNAs which regulate gene functions by targeting sequences in their 3' untranslated regions. Disruption of miRNA expression has been observed in various malignancies including skin cancers. Very little is known about the role of the miRNAs in the regulation of gene expression in response to UV irradiation in human skin. We generated a miRNA profile of UVB-irradiated normal human epidermal keratinocytes (NHEKs) selecting the physiologically relevant UVB dose of 40mJ/cm2. In our preliminary microarray experiments, we identified a subset of 44 miRNAs that were significantly (p< 0.05) differentially expressed in NHEKs, 4 h post UVB exposure. This data was further validated by qPCR which revealed a total of 22 miRNAs that were modulated by UVB. Additional statistical testing showed miR-30, miR-24 and miR-222 to be significantly modulated in both experimental systems. Studies in 3-D epidermal constructs exposed to UVB irradiation confirmed monolayer cell culture findings and demonstrated significant downregulation of miR-30. Our data indicate a potential role of miR-30 in the UVB exposed human skin. The hypothesis we test here is that UVB-mediated decrease in miR-30 expression results in loss of inhibitory control of proliferative pathways implicated in the pathogenesis of human skin cancer. After establishing the involvement of miR-30 in UVB induced skin response, we will shortlist the target genes of miR-30, employing mRNA microarray platform and computational target prediction sites. Functional studies will be conducted to verify miR-30 targets with potential role in UV-induced response using miRNA gain- and loss-of-function experiments. These results will be validated in a multilayered, highly differentiated, 3-D human epidermal skin model closely simulating human skin. For in vivo relevance of our in vitro data, we will examine miR-30 and its target genes in human skin specimens and study a possible correlation between miR-30 expression levels and the occurrence of skin cancer. Our study will provide in-depth understanding of the functions of miR-30 in the human skin and delineate its role in UV- induced skin cancer.